This application claims the priority of International Application No. PCT/DE2009/001578, filed Nov. 7, 2009, and German Patent Document No. 10 2008 056 652.7, filed Nov. 10, 2008, the disclosures of which are expressly incorporated by reference herein.
The present invention relates to a mask for kinetic cold gas compacting comprising a body for covering a not-to-be-coated region of a substrate to be coated having a work side exposed to the coating substance as well as a method for kinetic cold gas compacting in which a corresponding mask is used.
Kinetic cold gas compacting or kinetic cold gas spraying is known from the prior art for coating materials and in particular also components of gas turbines or aircraft turbines. Kinetic cold gas compacting is described in U.S. Pat. No. 5,302,414 for example. The method is characterized in that coating material in the form of a powder is moved onto the to-be-coated substrate by means of a carrier gas at high speed, but at temperatures below the melting point of the coating substance, wherein when the coating particles strike, the particles, just like the surface region of the to-be-coated substrate, deform due to the high speed so that the materials coalesce and the coating material adheres to the substrate.
Correspondingly, conventional coverings, such as adhesive tape coverings or silicone masking like those used in thermal spraying for example, are not adequate, because they are not able to bear up against the high particle speed.
On the other hand, stable materials, such as metal or plastic for example, are themselves coated so that a solidly adhering coating is produced on the mask making it necessary for these masks to be removed.
This problem was addressed in German Patent Application DE 10 2008 025510.6. The solution proposed there provides for the covering device to be provided with a structured surface, wherein the surface of the mask is configured such that the surface encloses an acute angle with the impact direction of the particles so that the impacting particles do not adhere to the mask, but are merely deflected.
Although this solution is already supplying good results, there is a further need for alternative solutions for corresponding masks for kinetic cold gas compacting which are potentially simpler to manufacture.
The object of the present invention is therefore making available a mask for kinetic cold gas compacting and/or a corresponding method for kinetic cold gas compacting, in which the problems of the prior art are overcome and in particular multiple-use masks are made available, which make possible both simple manufacturing as well as simple use.
The present invention starts with the knowledge that adhesion of the coating substance, i.e., of the particles striking the to-be-coated substrate in an unmelted state at a high speed, on the mask only takes place if the adhesion mechanism on which kinetic cold gas compacting is based is able to occur. This requires that both the impacting particles as well as the surface be deformed plastically in order to guarantee mutual coalescing of the materials and therefore adhesion of the materials. Correspondingly, the invention starts here and proposes a mask, which is configured to be hard on the side facing the coating source, i.e., the work side, in such a way that no surface deformation, i.e., no plastic deformation of the work side, is able to take place during the kinetic cold gas compacting that is used. This prevents the surface material of the mask and the impacting coating particles from deforming and coalescing and thus forming an adhering layer.
Because only the corresponding work side of the mask must have the required hardness, the mask may either be configured such that there is a hard coating on the work side or a correspondingly formed edge region or that the mask as a whole is configured with a corresponding hardness, wherein the mask may then be configured homogenously over the thickness.
To achieve a sufficient hardness on the work side a case-hardened or nitride-hardened steel or a corresponding hard material may be provided.
In particular, the mask may be case-hardened or nitride-hardened on the work side. If the mask is not through-hardened, there would then be a steel in the region of the base body suitable for case hardening or nitride hardening, while the surface region of the work side would be correspondingly age-hardened.
The hard material for forming the mask or for forming a hard surface layer on the work side of the mask may be formed of diamond, diamond-like carbon, cubic boron nitride, silicon carbide, aluminum oxide, boron carbide, tungsten carbide, vanadium carbide, titanium carbide, titanium nitride and/or zirconium dioxide or combinations thereof.
In addition, the hard material may also be enriched in a corresponding surface. In particular, Cr3C2—NiCr, Co28Mo18Cr3,5Si (T800) or the like may be used as a material for the hard work side.
Additional advantages, characteristics and features of the present invention are made clear in the following detailed description of exemplary embodiments on the basis of the enclosed drawings. The drawings in this case show the following in a purely schematic manner: